Systems for converting an image, such as characters of a document, into electrical signals which can either be stored in a memory for later recall or which can be transmitted to a remote location over, for example, telephone communication or similar systems, are well known in the reproduction art. Systems of this type have generally been referred to as line scanners. In one type of line scanner, the document is held stationary and a photodetector of an array of photodetectors are scanned across each line of the document along with a localized light source. In another type of scanner, the array of photodetectors and light source are held stationary and the document is moved therepast. In both types of systems, as the document is scanned, the high optical density or dark portions of the document reflect less light from the light source for reception by the photodetectors than the low optical density or light portions. As a result, the high and low optical density portions can be contrasted by the photodetectors for generating electrical signals representative of the image on or other surface characteristic of the document.
While systems of the type described above have been generally successful in fulfilling their intended purposes and have found commercial acceptance, these systems exhibit several deficiencies. The deficiency specifically addressed in the subject patent application deals with the fact that in a contact-type of line scanning system, the array of light sensitive elements is in constant abrasive contact with the image-bearing document. In other situations, a line scanning system, even if not of a contact-type, but which relies upon an array of light sensitive elements, is likely to be employed in an environment wherein acidic, corrosive or other deleterious gases could detrimentally affect the semiconductor alloy material from which those elements are fabricated and hence the performance of the array. By depositing any of the protective coatings described hereinafter immediately atop said elements, the problems associated with such abrasive and corrosive environments have been substantially eliminated.
These and other objects and advantages of the subject invention will become apparent from a perusal of the detailed description of the invention, the drawings and the claims which follow.